175 lines
5.0 KiB
Go
175 lines
5.0 KiB
Go
// Copyright 2019 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package localstore
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import (
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"context"
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"sync"
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"time"
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"github.com/ethereum/go-ethereum/log"
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"github.com/ethereum/go-ethereum/metrics"
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"github.com/ethereum/go-ethereum/swarm/chunk"
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"github.com/ethereum/go-ethereum/swarm/shed"
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"github.com/ethereum/go-ethereum/swarm/spancontext"
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"github.com/opentracing/opentracing-go"
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olog "github.com/opentracing/opentracing-go/log"
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)
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// SubscribePush returns a channel that provides storage chunks with ordering from push syncing index.
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// Returned stop function will terminate current and further iterations, and also it will close
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// the returned channel without any errors. Make sure that you check the second returned parameter
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// from the channel to stop iteration when its value is false.
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func (db *DB) SubscribePush(ctx context.Context) (c <-chan chunk.Chunk, stop func()) {
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metricName := "localstore.SubscribePush"
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metrics.GetOrRegisterCounter(metricName, nil).Inc(1)
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chunks := make(chan chunk.Chunk)
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trigger := make(chan struct{}, 1)
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db.pushTriggersMu.Lock()
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db.pushTriggers = append(db.pushTriggers, trigger)
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db.pushTriggersMu.Unlock()
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// send signal for the initial iteration
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trigger <- struct{}{}
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stopChan := make(chan struct{})
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var stopChanOnce sync.Once
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go func() {
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defer metrics.GetOrRegisterCounter(metricName+".done", nil).Inc(1)
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// close the returned chunkInfo channel at the end to
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// signal that the subscription is done
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defer close(chunks)
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// sinceItem is the Item from which the next iteration
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// should start. The first iteration starts from the first Item.
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var sinceItem *shed.Item
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for {
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select {
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case <-trigger:
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// iterate until:
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// - last index Item is reached
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// - subscription stop is called
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// - context is done
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metrics.GetOrRegisterCounter(metricName+".iter", nil).Inc(1)
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ctx, sp := spancontext.StartSpan(ctx, metricName+".iter")
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iterStart := time.Now()
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var count int
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err := db.pushIndex.Iterate(func(item shed.Item) (stop bool, err error) {
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// get chunk data
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dataItem, err := db.retrievalDataIndex.Get(item)
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if err != nil {
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return true, err
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}
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select {
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case chunks <- chunk.NewChunk(dataItem.Address, dataItem.Data):
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count++
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// set next iteration start item
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// when its chunk is successfully sent to channel
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sinceItem = &item
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return false, nil
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case <-stopChan:
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// gracefully stop the iteration
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// on stop
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return true, nil
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case <-db.close:
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// gracefully stop the iteration
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// on database close
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return true, nil
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case <-ctx.Done():
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return true, ctx.Err()
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}
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}, &shed.IterateOptions{
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StartFrom: sinceItem,
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// sinceItem was sent as the last Address in the previous
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// iterator call, skip it in this one
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SkipStartFromItem: true,
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})
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totalTimeMetric(metricName+".iter", iterStart)
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sp.FinishWithOptions(opentracing.FinishOptions{
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LogRecords: []opentracing.LogRecord{
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{
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Timestamp: time.Now(),
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Fields: []olog.Field{olog.Int("count", count)},
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},
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},
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})
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if err != nil {
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metrics.GetOrRegisterCounter(metricName+".iter.error", nil).Inc(1)
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log.Error("localstore push subscription iteration", "err", err)
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return
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}
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case <-stopChan:
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// terminate the subscription
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// on stop
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return
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case <-db.close:
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// terminate the subscription
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// on database close
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return
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case <-ctx.Done():
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err := ctx.Err()
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if err != nil {
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log.Error("localstore push subscription", "err", err)
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}
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return
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}
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}
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}()
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stop = func() {
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stopChanOnce.Do(func() {
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close(stopChan)
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})
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db.pushTriggersMu.Lock()
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defer db.pushTriggersMu.Unlock()
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for i, t := range db.pushTriggers {
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if t == trigger {
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db.pushTriggers = append(db.pushTriggers[:i], db.pushTriggers[i+1:]...)
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break
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}
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}
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}
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return chunks, stop
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}
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// triggerPushSubscriptions is used internally for starting iterations
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// on Push subscriptions. Whenever new item is added to the push index,
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// this function should be called.
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func (db *DB) triggerPushSubscriptions() {
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db.pushTriggersMu.RLock()
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triggers := db.pushTriggers
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db.pushTriggersMu.RUnlock()
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for _, t := range triggers {
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select {
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case t <- struct{}{}:
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default:
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}
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}
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}
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